Sealing element



y 1968 T. WIBERG 3,392,789

SEALING ELEMENT Filed Aug. 23, 1966 FIGI. 9

INVENTOR1 TOR E WIBERG ATTYS United States Pate htfo.

2 Claims. (Cl.170160.23)

ABSTRACT OF THE DISCLOSURE A sealing element for an axial fan with a variable pitch blade. The fan has a hub through which the blade projects and in which is provided a recess surrounding the blade shaft with a re-entrant surface substantially coplanar with the undersurface of the blade base plate. The sealing element is of generally U-shaped cross section and is mounted freely in the recess so that the centrifugal force of rotation of the hub engages one leg of the element against the re-entrant surface of the hub and other other leg of the element against the undersurface of the fan base plate, the web of the element being free to twist in the recess to permit relative displacement between the two surfaces axially of the blade shaft.

The present application is based upon Swedish application No. 13,914/ 65 filed October 28, 1965, the priority of which is claimed.

The present invention relates to a sealing element for axial fans with adjustable blades, and more particularly to a sealing element mounted in the impeller between the hub and the base plate of a blade which is rotatable in the hub.

Fans equipped with blades adapted to be adjusted while in operation comprise a number of mechanical elements in the hub for rotating the blades. In fans for dust-laden gases, it is important to protect such elements against dust, and to prevent the dust from penetrating into the clearance gap between the stationary and rotary parts.

Heretofore, flushing air was utilized for preventing dust from penetrating through the gap to the sensitive mechanical elements effecting the blade rotation. The flushing air was supplied under pressure to the interior of the fan hub, in such a manner that the direction of the air flow through the gap counteracts the penetration of the dust. Such an arrangement, however, is complicated and requires both a supply of flushing air from special fans or other pressure sources, and arrangements for directing the flushing air through the clearance gap.

A primary object of the present invention is to eliminate the disadvantages involved in the conventional seals in an impeller, and at the same time to produce an effective and simple seal between the hub and the blade base plates rotatably mounted in the hub when the impeller is rotating about the hub axis.

This object is achieved substantially by mounting a U-shaped sealing element in a recess in the hub having a reentrant surface substantially coplanar with the undersurface of the blade base plate, so that the web of the sealing element bridges the clearance gap between the base plate and the hub, and the legs of the element are 3,392,789 Patented July 16,v 1968 pressed by centrifugal force against said coplanarsu'rfaces.

As a further object of the invention, the sealing element must operate effectively also in the event of minor axial displacement between the stationary and the rotatable parts.

An embodiment of the invention is described in greater detail in the following description with reference to the accompanying drawing, wherein:

FIG. 1 is a cross section through a fan hub embodying a sealing element according to the invention;

FIG. 2 is an enlarged sectional view showing the sealing element according to the invention, the sealing surfaces for the hub and the blade base plate being in normal position; and

FIG. 3 shows the same detail as FIG. 2 with the sealing surfaces being displaced somewhat in relation to each other.

Referring to the drawing, in a hub 1, a circular blade base plate 2 and a blade 9 are connected to a shaft 10. Between the hub 1 and the blade base plate 2 there is formed a clearance gap 3 with a substantial rectangular cross section. In order to be prevent dust-loaded gas from penetrating into the interior parts of the hub, a recess 11 is formed in the huh I surrounding the blade shaft 10 below the base plate, in which a continuous sealing ring 4 is placed to bridge said gap 3. Said sealing ring 4 has U- shaped cross section, its webs 12 being plane and its legs having the form of rounded beads 7 and 8. Upon the rotation of the impeller, said beads are pressed by the centrifugal force against two sealing surfaces 5 and 6. One of the said surfaces 5 is a re-entrant surface formed in the hub 1 by the recess 11 and the other surface 6 is the undersurface of the blade base plate 2. The surfaces 5 and 6 are normally coplanar, but in actual operation, differences in position between the surfaces may arise. The sealing ring is made of an elastic flexible material, for example plastic, and clearance is provided below the web 12, so that the difference in position between the sealing surfaces 5 and 6 in axial direction are balanced by the twisting of the sealing ring (see FIG. 3).

While a particular embodiment of the invention has been illustrated and described herein, it is not intended to limit the invention to such disclosure, but changes and modifications may be made therein and thereto within the scope of the following claims.

I claim:

1. In an axial fan having a rotary hub, a fan blade, and a shaft mounting said blade for rotation about its axis within said hub, said blade being mounted on a circular base plate extending radially outward from said shaft and providing a clearance gap between said plate and said hub, the improvement wherein said hub is provided with a recess surrounding said shaft below said gap and having a re-entrant surface substantially coplanar with the marginal undersurface of said base plate, and a sealing element freely mounted in said recess comprising a ring having a U-shaped cross section with a plane web and bead-like legs projecting from the web, one of said legs projecting into engagement with said re-entrant surface and the other of said legs projecting into engagement sealing element bridges said clearance gap,---therotatien of said hub pressing said sealing element into sealing engagement with said surfaces by centrifugal force, the thickness of said Web being less than the thickness of said bead-like legs so as to twist and permit relative displacement of said legs axially of said shaft.

2. An axial fan according to claim 1 wherein said seal ing' element has a thickness less than the depth of said recess and is made of elastic flexible material to accommodate relative displacement of said surfaces axially of said shaft.

References Cited UNITED"'STATES PATENTS 6/1947 Lowy 170-160.23 2/1948 Sheets 170160.23 7/1950 Sharp 170160.23 1/1966 Fermer 230-4114 FOREIGN PATENTS 3/1962 Germany. 5/1938 Great Britain,

HENRY F. RADUAZO, Primary Examiner. 

